The background of the invention will be discussed in two parts.
1. Field of the Invention
This invention relates to infusion apparatus and more particularly to portable infusion apparatus which may be carried on the person of an ambulatory patient without connection to an external power source.
2. Description of the Prior Art
Infusion apparatus for ambulatory patients requires that the apparatus be of lightweight for carrying by the patient. Preferably such devices include some battery operated mechanism for actuation of means for discharging fluid at a controlled rate to a maximum amount over a treatment period to a patient, usually by intravenous means.
One such apparatus is shown and described in U.S. Pat. Nos. 4,650,469 and 4,559,038, issued on Mar. 17, 1987 and Dec. 17, 1985, respectively, to Berg et at., both such patent being entitled "Drug Delivery System". A third companion case, U.S. Pat. No. 4,565,542 issued to Berg on Jan. 21, 1986, and is entitled "Locking Mechanism for a Drug Delivery System". The device in those patents is modularly constructed and relates to a drug delivery system for ambulatory patient use and includes a control module and an interlocking reservoir module. The reservoir module contains a drug container bag therein with the tube thereof supported longitudinally on a pressure plate. With the reservoir module connected to the control module, a motor controlled camshaft of a pumping mechanism reciprocates a plurality of valves and an expulsor in the control module for engaging and interacting with the tube located on the pressure plate for forcing the drug from the container bag to the patient.
Such a device requires a complex pumping and valving mechanism which complexity adds to both weight and cost. Furthermore, since the reciprocating valves act against the external surface of the elastomeric tube, any variations in tube elasticity and wall thickness could conceivably affect the discharge rate and accuracy of the drug delivery system.
In accordance with an aspect of the present invention, there is provided a new and improved modular infusion apparatus with a new and improved fluid delivery system of economical construction which operates on the fluid rather than the delivery tube.
In accordance with another aspect of the invention, the controls for setting the variables needed for the dispensing of solution are positioned in such a way as to be concealed and inaccessible during use by the patient.
Another feature of the invention relates to the interlocking arrangement between the cassette and the control module.